Abstract: A multi-chamber basin is sized to collect excess waste water exceeding the processing capacity of a sewage system. In order to disinfect the waste water exceeding the basin capacity, disinfectant is added at a point in the system after the first basin. After the rain event is over and there is excess sewage treatment capacity, the sewage treatment in the multi-chamber basin is returned to the sewage system. By not disinfecting the waste water in the first basin chamber, the overall disinfectant usage can be minimized.

Abstract: A back-water trap unit comprises a housing having an outer perimetric wall sealed to a base to define an enclosure, and a removable housing cover comprising inlet apertures. An interior wall, shorter than the housing wall, is sealed to the base to define an inner compartment and an outer compartment within the enclosure, the inner compartment being sealed by a cover secured to the upper interior wall edge and the inside of the housing wall. A flapper valve secured to the interior wall within the inner compartment is rotatable in response to liquid pressure to open or close an inlet aperture proximate the lower interior wall edge. An outlet through the housing wall as high as or above the upper edge of the inlet aperture allows discharge of fluid from the inner compartment, while the flapper valve prevents unwanted back-flow from the inner compartment to the outer compartment.

Abstract: A system and related method for separating floating and nonfloating particulate and entrained, suspended, and/or dissolved contaminants from a fluid. The system includes a tank with a lower chamber spaced from an outlet or upper chamber by a confinement deck. The deck includes one or more sockets for receiving one or more filter units for fluid treatment. In addition, the lower chamber of the tank acts as a pretreatment sump to remove floating and nonfloating particulates, thereby reducing the load on the filter units. The filter units are configured for radial and/or upward flow of the fluid from the lower chamber. The filter units may include one or more filter media through which the fluid pass prior to exiting the tank. The filter units include a removable screening retainer for retaining the filter media and/or to screen relatively large contaminants. The filter unit may be removed for ease of tank maintenance and replacement of filter media.

Abstract: The present invention is a storm water filter system for filtering floatable debris and non-floating pollutants from storm, water passing through a storm water drain system vault. The storm water filtering system has a vault having chamber having a floating skimmer panel between the inlet thereto and the outlet therefrom. The skimmer panel has a filter passageway therethrough for filtering the storm water while the floatable skimmer panel captures floatable debris and trash from the storm water. Storm water entering the vault inlet passes through a filter element in the skimmer panel and out the vault outlet and also can pass under the floating skimmer panel when the floatable skimmer panel is floated to a raised position to thereby prevent storm water from accumulating on the inlet side of the wall.

Abstract: A water tank apparatus comprising a first tank (100) for wastewater collection; a second tank (200) for collection of rainwater and groundwater; a third tank (300) connected on the downstream side of the first tank (100) and second tank (200); and a fourth tank (400) disposed at a high position above the ground and connected on the downstream side of the third tank (300) so as to supply any reserved water as a usable water, wherein the first tank (100) and second tank (200) are individually partitioned into first sections (102,202) and second sections (103,203), and wherein the second sections (103,203) are provided with ramps for water flowform its upstream side superior area toward inferior area, the ramps furnished with a multiplicity of projections.

Abstract: A flocculate dosing tray apparatus for placement in a storm water drain inlet under the inlet grate captures water entering the storm water drain inlet and dispenses a flocculate into the water for treatment of the interior storm water as the storm water enters the storm water drain system.

Abstract: A stormwater treatment system, including a treatment container for treating stormwater through a bioretention mechanism. The treatment chamber includes an overflow/bypass system, including a flow distribution tray or flume that includes a distribution compartment or channel, an overflow dam or weir, and an overflow/bypass compartment. The stormwater distribution compartment or channel includes one or more openings for stormwater to be treated to fall onto the filter media located within the treatment container. When high flow rates are obtained that exceed the capacity of the unit, the overflow/bypass stormwater enters the overflow/bypass compartment where it is received by an overflow/bypass outlet pipe to be directed out of the container without such water being treated or further treated by the filter media.

Abstract: A bioretention system and method are provided for removing phosphorus, nitrogen and other materials from effluent such as wastewater and stormwater. The system and method can include a filtration media comprising water treatment residuals and other fill such as soil. Plants can be growing in the soil. The system can also include a drainage system to regulate outflow, to function during both low and high throughputs of water.

Abstract: In a rotary brush screen at an overflow sill of a rainwater relief system, comprising screen bars extending transverse to the overflow sill and strippers engaging in the screen bars in a comb-like manner, the strippers are put into a curvilinearly extending, circling movement via a crank drive in accordance with the invention by means of an actuating lever in cooperation with a stationary support bearing, due to which circling movement the strippers are guided from above into the spaces between the screen bars and out again at the bottom of the overflow sill. The risk of the discharge of solids into the waters as a result of a mechanical influence on the solids during the stripping operation is reduced thereby and the operational safety is increased.

Abstract: Non-limiting embodiments disclosed herein include components of a rain water collection system and methods of fabricating the components. The disclosed components include a down spout interface bladder and a rain water holding device. Also disclosed are a method of fabricating a down spout interface bladder and a method of fabricating a rain water holding device.

Abstract: An elevated swale comprising a porous and water-permeable interior zone, a permeable and compressible exterior shell, and vertically oriented cylindrical inserts. The exterior shell surrounds the interior zone, and the cylindrical inserts are placed within cylindrical cavities that are cut vertically into the interior zone. In an alternate embodiment, the present invention is an elevated swale comprising stacked layers of polymer matting and vertically oriented cylindrical inserts. The cylindrical inserts are placed within cylindrical cavities that are cut vertically into the stacked layers of polymer matting.

Abstract: Methods, systems, drain vaults, and tools are employed to treat storm water runoff from a watershed. The methods and system may include multiple drain vaults that function to receive and allow quiescence of the water so that laminate flow may be achieved between adjacent vaults. The drain vaults may be made of stacked together vault sections held in compression, and screens and arrays of tube elements are with different drain vaults. There may be combined systems where in an upstream system flow is uncontrolled during a rainstorm and some of the rainfall water is diverted to a retention structure and then in a control flow rate is transferred to a downstream treatment system that may use tube elements. A tool is used to clean the tube elements.

Abstract: A wastewater treatment system for treating excess wastewater from a sewer system includes a container having first and second portions adapted to receive excess wastewater from the sewer system, and a generally horizontally oriented screen arrangement disposed in the second portion of the container. The system further includes a treating agent dispenser for introducing a treating agent into the wastewater, and an effluent passage in fluid communication with the second portion of the container. During a sufficient rain event, the wastewater flows from the sewer system into the container, through the screen arrangement, and then into the effluent passage, such that the wastewater flows generally in a first direction through the first portion of the container, then generally in a second direction different than the first direction through the second portion of the container.

Abstract: A hood for mounting over an outlet in a wall of a catch basin is disclosed. The hood includes a hood wall that forms a prow in a horizontal plane. The prow extends along an axis of the hood thereby achieving optimal flow conditions in the catch basin. In some embodiments the hood wall is shaped to be at least partially sealably mounted to the interior wall of a catch basin have a circular cross section in a horizontal plane. This novel hood shape facilitates installation of the hood in the circular catch basin, while also reducing the flow of oil and other pollutants into the outlet pipe in the circular catch basin. In some embodiments a perforated screed is also disclosed that surrounds the hood to aid in the capture of floatable pollutants.

Abstract: A modular filter system for use within a pollution removal structure. The system includes a plurality of modular filters that can be nested together forming a common passageway that passes through all of the nested filters. With normal runoff, the water passes laterally through the filters and enters the common passageway to exit the structure. In the event of a high flow of runoff, an overflow pipe conveys water directly to a downstream storm drain by-passing the filter system. The overflow is created by either: a) allowing the water to rise above the upper surface of the upper modular filter and directly into the common passageway or b) by overflow pipes which connect to a downstream pollution removal structure; or a combination of paths a) and b). By using nested filters, the number of filters nested together can be customized in accordance with the depth of the particular storm drain.

Abstract: A drainage system for a synthetic sports field is disclosed that substantially prevents the leeching of specific contaminants from surface runoff water from entering into water tables or sewer systems associated with the drainage of the synthetic sports field. The drainage system includes a containment system and filtration system located beneath the synthetic sports field for directing rainwater through a series of drains and filters prior to being exposed to either the sewer system or water table. In this way, environmental concerns associated with the drainage of synthetic sports fields is alleviated.

Abstract: A method for processing water, including, collecting contaminated water from a first water collection site; collecting contaminated water from a second water collection site; transferring the contaminated water collected from the first and second water collection sites to a water treatment site; and processing the contaminated water to produce a processed water. Also, a system for processing rainwater, the system including a separation unit configured to receive a flow of rainwater from hardscape; a storage tank in fluid communication with the separation unit; a primary filtration unit in fluid communication with the storage tank; a secondary filtration unit in fluid communication with the primary filtration unit; an adsorption unit in fluid communication with the secondary filtration unit; and a disinfection unit in fluid communication with the adsorption unit.

Abstract: An apparatus for reducing pollution in wastewater that collects in a catch basin is disclosed. The apparatus includes a hood affixed to an interior wall of a catch basin over an outlet, and a skirted boom adjacent to at least a portion of said hood and fixed relative to the hood. The skirted boom includes an upper portion and a skirt extending down from the upper portion. The skirted boom is installed so that the upper portion of the skirted boom is adjacent to said hood at the static water level in the catch basin and the skirt extends downward, preferably below the bottom of the hood. A tether assembly for installing the apparatus and a method of using the same is further disclosed.

Abstract: Systems and methods for treating water passing through a catch basin may include first and second filters. In some embodiments, one or both of the filters can have a plurality of regions with different nominal flow rates.

Abstract: The present invention discloses a device with connecting member having an elastic ring, and the device includes a body having at least one accommodating cavity on the body and an exhaust opening on the internal periphery of each accommodating cavity; and at least one connecting member having an insert unit at an end of each connecting member, at least one positioning block at the periphery of the insert unit and at least one elastic ring sheathed onto the periphery of the insert unit, such that if the connecting member is inserted into the accommodating cavity, the shape of the accommodating cavity can accommodate the insert unit and each positioning block precisely.

Abstract: The present invention relates generally to purification and separation of a fluid flow stream, and more particularly, to a separation system including a device for dispersing the fluid flow and separating pollutants there from. The device includes a vertical screen and baffle wall positioned in a fluid flow stream between the inlet and outlet openings of a chamber. The chamber can include a sump for collecting and storing sediment that is separated from the fluid. The present invention also relates to a method of purifying and separating a fluid flow stream.

Abstract: Separator for removing impurities, especially smaller particles, from rain water. It comprises a first reservoir (2) and a second reservoir (6). The first reservoir (2) performs the function of removing the heaviest portions of the impurities, but is also provided with a lamellar device (4), wherein small drops and impurities of the rain water may be combined to larger impurity aggregates. The second reservoir (6) is divided into a first chamber (6a) and a second chamber (6b), said chambers communicating with each other. A tube (5) provided with perforations (5?) is arranged above the lamellar device (4), through which rain water containing impurities is able to flow from the first reservoir (2) and into the first chamber (6a). The first chamber (6a) is provided with a filter (9). In this way, a more efficient purification of rain water than using the known separator is provided.

Abstract: To facilitate cleaning and to facilitate management thereof, a dust-removal managing pit is provided with an upper pit having a bottom and to which an inflow pipe is connected and a cylindrical lower vertical pit having its upper part connected to the upper pit for supplying water flowing down from an upper-end opening portion to a water storage tank. The upper end of the lower vertical pit is provided penetrating a bottom wall of the upper pit, while a peripheral wall of the upper pit is provided so as to surround the upper end of the lower vertical pit, and a peripheral groove for precipitating solid substances contained in water is formed between the periphery of the upper end of the lower vertical pit and the peripheral wall. A mesh plate constituted capable of filtering water leading to the peripheral groove is provided on the upper pit. One end of a drain pipe with the other end connected to a sewer pipe is connected to the peripheral wall, and an adjusting valve is provided in the drain pipe.

Abstract: A system of water collecting, cleaning, and storing comprises a top-opened water storing container (1), with the wall of which a watertight structure; a collecting well (2) provided in the water storing container (1), which has a lid (6) and has a wall of permeable structure through which water exchange between the water storing container (1) and the collecting well (2) is achieved; filling elements (4) filled between the collecting well (2) and the water storing container (1), on top of which a pervious surface layer (5) is paved.

Abstract: A novel method to filter stormwater in existing and new facilities. The system is generally an insert or series of inserts which include lightweight aggregate (“LWA”) in a manner such that the aggregate is retained in the insert. The insert includes openings to allow water to flow into the insert and through the LWA such that contaminants are captured by the aggregate and removed from the water which exits the insert.

Abstract: A large vault or tank receives the runoff water to be cleaned. There are one or more small tanks in the large tank (vault). Each small tank is inverted and receives water at its open lower end, from the large tank. The water entering the small tank rises, as the water level in the large tank rises, and flows upward through a filter. When the water level rises above the top of the filter it enters an outlet tube or pipe and then flows downwardly along the center-line of the filter. A float, a valve and a check valve may cause the system to function as a siphon and feed the filtered clean water to an outlet. Alternatively the siphoning effect will occur if the inside diameter of said outlet tube is small enough to form a partial vacuum.

Abstract: A method and apparatus for the removal of metals and cleanup of roof top storm water runoff comprising a drum structure which includes at least two media beds for filtering the storm water runoff. The first media bed filters out particles of toxic metals and metal ions are absorbed on the media material in the first media bed.

Abstract: A storm drain relief channel for providing fluid/debris access from the surface of a road to the interior portion of a catch basin including a rigid box structure includes a substantially-hollow channel structure disposed adjacent to the rigid box structure of a curb inlet, the substantially-hollow channel structure having a first end defining a first opening and a second end defining a second opening, wherein the first end is configured to be disposed adjacent to and substantially flush with, and in fluid/debris communication with, the surface of the road and the second end is configured to be disposed one of adjacent to and within, and in fluid/debris communication with, the interior portion of the curb inlet.

Abstract: A granular filter media dry cell (or filter or bed) for dewatering a liquid composition of water and particulate solids. The liquid composition is applied to the granular filter media to remove water from the liquid composition by passing through the granular filter media with the particular solids collecting on top surface of granular filter media. Water is first allowed to fill from below to just above the top layer of the filter media. A non-porous liner is located on the inner, bottom surface of the container. A drain pipe, having small openings, is located on top of the liner in the valley. A porous layer of large filter media, with the drain pipe therein, is located in the bottom of the container. A grid having open passageways, with fine filter media therein, is located on top thereof. A layer of fine filtrate sand is located on top of the grid.

Abstract: The present invention provides a method and apparatus for the treatment of waste water, particularly for the treatment and/or reduction of floating pollutants in storm water waste streams. The apparatus of the invention achieves a high containment level of floating pollutants compared to conventional oil/gas traps available for catch basin use. In a preferred embodiment, the device of the invention is a catch basin trap that arrests the flow of pollutants, particularly floating pollutants. The trap is designed and installed in such a manner that a sealed system is created, ensuring that all fluid flow (e.g., storm water discharge) must pass through the trap and cannot bypass the trap due to unreliable trap attachment mechanisms or unsealed joints. Containment of floating pollutants is achieved.

Abstract: The invention is directed to a water purification system to remove pollutants from surface run-off water that has flowed into storm water drainage channels. A tank having an open reservoir region is positioned in the drainage channel or adjacent to the channel so as to permit water to flow through an upstream port of the tank and pool within the open reservoir region. The tank has a downstream port through which water pooled within the reservoir region may flow if the level of the pooled water sufficiently increases as a result of a rise in the flow level of the water in the drainage channel. The open reservoir region contains bioremediation plants having the physical property of removing pollutants from the pooled run-off water contained in the reservoir region.

Abstract: A temporary culvert barrier for placing across the mouth of a culvert for blocking litter and debris from entering or exiting the culvert and for filters to block silt or sand from clogging the culvert or the drain area. The filters may also be selected to absorb oils salts or other chemicals. The temporary barrier is easy to install and remove. The barrier plates and filters fit to the size of the culvert mouth and have adjustment slots for different width mouths. The culvert barrier may be used to prevent pollution at construction sites and be temporarily or permanently attached to culvert mouths. The filters may be changed or cleaned as required.

Abstract: The present invention is uniquely engineered and provides water treatment devices for treatment of water in a small community or individual who are out of reach of access to safe water for domestic use, reach of adequate resources and reside in rural setting. Water treatment device of the invention are flexible, light weight and have high capacity.

Abstract: A stormwater detention system includes a containment row for removing and collecting solids from stormwater. The containment row may be surrounded by a water-impermeable membrane, and designed to receive incoming water before other rows of the detention system. The containment row collects solids from the stormwater before the water is redirected into one or more additional rows, which are water permeable and buried in water permeable media. Filter structure may be associated with a flow system that delivers water from the containment row to the additional rows.

Abstract: A self-contained wetlands treatment system to remove pollutants from water and treat stormwater runoff or other grey water. This is system and method wherein the water is passed through a wetland filtering and treatment system. This invention removes solids, metals (dissolved/particulate), nutrients (dissolved/particulate), oils, and bacterial contaminants from the water. The system and system housing can be fabricated, built, and assembled in a broad range of sizes and materials to accommodate and treat a broad range of influent flow rates.

Abstract: Materials, compositions, substances and methods and systems for stormwater treatment in wet ponds, dry ponds and a green roof system. A first embodiment provides in-situ treatment unit within the retention pond by withdrawing the stored stormwater to circulate the stored stormwater into the in-situ treatment unit to sorb nitrogen from the stored stormwater. A second embodiment provides uses a riprap apron, a perforated riser located at the bottom of the riprap apron and a goetextile media encased in a sorption media jacket around the perforated riser. A third embodiment provides a green roof stormwater treatment system that includes protection for waterproofing and insulating the roof, a pollution control media layer for filtration and sorption of solids and dissolved materials found in stormwater, a growing media for growing vegetation, and a cistern to store the runoff stormwater between irrigation events.

Abstract: A stormwater filtration system includes a stormwater containment structure including a bottom surface, an inlet that receives stormwater and an outlet through which filtered stormwater exits the stormwater containment structure. A flow structure is at the bottom surface. The flow structure includes a conveyance conduit running along the bottom surface of the stormwater containment structure and in fluid communication with the outlet of the stormwater containment structure. The conveyance conduit includes a port extending through a sidewall of the conveyance conduit. A saddle includes an upper component and a lower component connected to the upper component such that the upper and lower components straddle the conveyance conduit at the port. The upper component includes an opening in communication with the port and the lower component supports the conveyance conduit above the bottom surface.

Abstract: A drainage catch basin is formed from a rectangular trough with a planar upper rim defined by at least two opposite sidewalls and includes at least one inner wall forming a lower rim to define the gutter opening for flush mounting with the curb. The basin is covered by a top with a planar bottom that preferably includes a central circular manhole cover. The top is preferably formed by first providing a mold having a bottom and side frame of steel plates reinforced by a galvanized steel nosing and crossing rebar. The mold is then filled by concrete casting while installed on the catch basin trough to match the exterior color and/or finish of the adjacent sidewalk, street and/or curb.

Abstract: A separator tank for separating and trapping contaminants in rainwater and runoff is disclosed. According to one embodiment of the present invention, the separator tank comprises a container having a bottom wall, side wall, and top wall defining an internal chamber; an insert located inside of the internal chamber, the insert comprising a weir defining an intake area between the weir and the side wall; and a round-edged orifice positioned within the intake area; an inlet conduit for introducing an influent liquid into the intake area; wherein the weir is positioned such that the weir induces the influent liquid to flow in a swirling motion within the intake area. According to another embodiment of the present invention an insert for a separator tank is disclosed. The insert includes a weir defining an intake area for receiving an influent liquid; and a round-edged orifice positioned within the intake area.

Abstract: Systems and methods for treating water passing through a catch basin may include first and second filters. In some embodiments, the filters each have a plurality of regions with different nominal flow rates.

Abstract: An oil-water separator for use in a trench, which surrounds an oilfield. The separator is positioned in the ground such that an inlet conduit extends at about the same level as the bottom of the trench. The trench water is admitted into the housing, where it contacts a plurality of buoyant oil-absorbing members, causing the oil particles to adhere to the surface of the oil-absorbing members. An outlet conduit located downstream from the oil-absorbing members is connectable to a pump to cause the oil-free water to be pumped from the housing and diverted away from the trench.

Abstract: In some embodiments, a filtration system may include one or more of the following features: (a) a housing having a bottom portion, a middle portion coupled to the bottom portion and all upper portions and a cap coupled to the upper portion, (b) a sediment storage area within the bottom portion, (c) a separator area within the middle portion, (d) a porous filter within the upper portion, (e) an access hatch within the cap, (f) an inlet pipe for allowing storm water within a middle chamber, (g) an outlet pipe for allowing filtered water to be discharged from the filtration system, and (h) a central pipe being a passageway through the porous filter.

Abstract: A debris cage is disclosed. The debris cage may include multiple panels, each having a plurality of opening. Each of the panels may be fastened together to form an enclosed structure having a substantially cylindrical portion integral with a conical or dome-like portion at a terminating end of the enclosed structure. Each of the panels may have various shaped openings facilitating the flow of fluid while potentially impeding debris from passing through the debris cage.

Abstract: A liquid purification and separation apparatus for separation of pollutants in stormwater runoff is disclosed. This apparatus utilizes gravitational separation and tortuosity, resulting from a plurality of baffles both perpendicular to and oblique to the primary water flow direction, to trap substances less-dense and more-dense than water. The apparatus features improved resistance to pollutant remobilization through treatment of water volume rather than flow rates, using vertically stacked water columns of varying depths to settle small particles. An overflow structure diverts excessive liquid without interfering with purification and separation, and can be placed integrally within or external to the apparatus receptacle.

Abstract: A stormwater filtration system includes a stormwater containment structure including a bottom surface, an inlet that receives stormwater and an outlet through which filtered stormwater exits the stormwater containment structure. A flow structure is at the bottom surface. The flow structure includes a conveyance conduit running along the bottom surface of the stormwater containment structure and in fluid communication with the outlet of the stormwater containment structure. The conveyance conduit includes a port extending through a sidewall of the conveyance conduit. A saddle includes an upper component and a lower component connected to the upper component such that the upper and lower components straddle the conveyance conduit at the port. The upper component includes an opening in communication with the port and the lower component supports the conveyance conduit above the bottom surface.

Abstract: A stormwater filtration system includes a stormwater containment structure including a bottom surface, an inlet that receives stormwater and an outlet through which filtered stormwater exits the stormwater containment structure. A flow structure is at the bottom surface. The flow structure includes a conveyance conduit running along the bottom surface of the stormwater containment structure and in fluid communication with the outlet of the stormwater containment structure. The conveyance conduit includes a port extending through a sidewall of the conveyance conduit. A saddle includes an upper component and a lower component connected to the upper component such that the upper and lower components straddle the conveyance conduit at the port. The upper component includes an opening in communication with the port and the lower component supports the conveyance conduit above the bottom surface.

Abstract: In some embodiments, a filtration system may include one or more of the following features: (a) a housing having a bottom portion, a middle portion coupled to the bottom portion and an upper portion, and a cap coupled to the upper portion, (b) a sediment storage area within the bottom portion, (c) a separator area within the middle portion, (d) a porous filter within the upper portion, (e) an access hatch within the cap, (f) an inlet pipe for allowing storm water within a middle chamber, (g) an outlet pipe for allowing filtered water to be discharged from the filtration system, and (h) a central pipe being a passageway through the porous filter.

Abstract: A gutter member includes an inlet operatively coupled to a gutter trough. The inlet is configured to receive matter such as water and non-water matter from the gutter trough. The gutter member further includes an outlet operatively coupled to a top of a downspout. The outlet is configured to pass water to the downspout. The gutter member further includes a reservoir configured to collect non-water matter. The reservoir is located between the inlet and the outlet and is lower than the gutter trough relative to the earth. The reservoir includes an exit port door configured to move between a first position in which a substantial amount of the non-water matter is retained in the reservoir and a second position in which the non-water matter is released from the reservoir.

Abstract: A stormwater treatment system including a substantially water impermeable treatment container for treating stormwater through a bioretention mechanism. The treatment container includes an overflow/bypass opening to receive stormwater that bypasses the treatment container filter media, or is only partially treated as a result of high stormwater flows in excess of the capacity of the container to treat the stormwater. The stormwater is directed into the container through an inlet, such as an inlet pipe, preferably connected to a roof drain system for processing and treating stormwater from the roof of a building. The overflow/bypass opening may be adjacent the top wall or bottom wall of the container.

Abstract: A cubic modular subsurface stormwater unit has equal top and bottom surfaces spaced apart by a set of four pillars, each of which runs from a corner of the top surface to a corresponding corner of the bottom surface. The pillars define a void having a generally cruciform cross section, the void opening onto each of the four side faces defined between the roof and the base. A line of units connected together in series side to side will have a long throughway formed by the respective voids in each unit, and a regular matrix of X- and Y-axis throughways will be formed as units are connected laterally on all sides. The unit is formed of identical halves which can be connected together in any orientation due to the square configuration and to a mating connection which has mating parts symmetrically disposed about a diagonal corner-to-corner line.